链表中倒数第k个结点

让快指针先走k-1步，如果快指针走到尾，就结束
然后快慢指针同时走



https://www.nowcoder.com/practice/529d3ae5a407492994ad2a246518148a?tpId=13&&tqId=11167&rp=2&ru=/activity/oj&qru=/ta/coding-interviews/question-ranking

struct ListNode* FindKthToTail(struct ListNode* pListHead, int k ) 
{
    if(pListHead==NULL||k==0)
    {
        return NULL;
    }
    struct ListNode*fast=pListHead;
    struct ListNode*slow=pListHead;
    while(k>1)
    {
        fast=fast->next;
        if(fast==NULL)
        {
            return NULL;
        }
        k--;
    }
    while(fast->next)
    {
        slow=slow->next;
        fast=fast->next;
    }
    return slow;
    // write code here
}